I have done this many times. U might have a hard time with the bolts being rusy so spray some wd-40 on em. If they will still not budge like the ones on my 75 f-250 you might have to grind the heads off the bolts inside the bed. BECAREFUL and use a steady hand so u dont damage the bed if u must take that route. Have a couple of guys to help u lift it off.
Another product i'd recommend is KROIL made by Kano Laboratories . I work at a gas station, and the mechanic says that KROIL is the best product out of the penetraiting oil, PB Blaster and WD40. We order the stuff by the case. Might try it out.
the bolts on the s-10s do not go thru the bed of the truck. the bolt into the support rails on the bottom side of the bed. I have body dropped many of these trucks and I personaly have never had a problem getting the bolts off with only a socket and breaker bar, any other questions on s-10s I might be able to answer because i have dissassembled alot of these for dropping.
The bed is attached the same way as on my dodge. I had to snap the heads off and when it was off i flipped it over and drilled out the holes then i just used bolts, and nuts with lock washers instead of retapping the holes. seems to work just fine.
When installing a hitch on my 89 chevy 1500 I had to remove two bolts. One snapped off with the impact wrench, but the other didn't. I tried PB blaster, but that failed. I endud up cutting if off with the sawzall.